healthHealth and Medicine

Here's What Happens To The Human Body If It Overheats


Jonathan O'Callaghan

Senior Staff Writer


Large parts of the world have spent the last year on fire as the effects of the climate crisis kick in. Record temperatures were broken across the world, and 2020 is set to be one of the five hottest years on record. But what actually happens to your body as the temperature increases? Here, we’ll talk through some of the ways the human body struggles in heat, and measures you can take to protect yourself against it.

37°C (98.6°F)


The processing center of our brains, the hypothalamus, is constantly trying to keep our bodies at a constant 37°C (98.6°F). Temperature receptors in the skin can help monitor the temperature, and when it rises, it calls into action.

As we get hot, our brains send nerve impulses to our skin to start sweating, in turn sending blood to the skin’s surface. Through evaporation this increases heat loss in an attempt to cool us.

In conditions where the temperature is not too hot, the body can also lose heat through “dry heat loss” – as the temperature of our skin is warmer than the surrounding environment.

But when temperatures surpass 37°C, things get tricky.


38°C (100.4°F)

By some measures, your skin needs to be below 35°C (95°F) to get rid of heat efficiently, so when temperatures approach 37°C or above, your body struggles.

When you go above 37°C, your sweating will get more intense and you will get more and more tired as your muscles slow down. Nausea can increase to a point where you start vomiting and succumb to diarrhea.

If you lose too much liquid as a result of sweating, then you may even experience something called heat syncope, the result of a halt in blood flowing to the brain. In more simple terms, you will faint as your body struggles to cool itself. If you sweat too much, you may also get red spots on your skin where pores become blocked, causing a rash.


And it’s not just the temperature you need to worry about. Another major factor is humidity. The more humid it is, the harder it is for your body to lose heat via sweating. If your body gets too hot, your organs will literally start cooking and could fail.

Your organs can start to fail if your body gets too hot. Komsan Loonprom/Shutterstock

39°C (102.2°F)

If temperatures rise to about 39°C (102.2°F), then the body can no longer lose heat via dry heat loss. So it orders the muscles to slow down, which causes fatigue.

On a hot day, you’ll sweat out a lot of water, but even if you drink to avoid dehydration, you can experience a decrease in electrolytes. This will create a salt imbalance that leads to cramps.


Rising heat can also result in confusion and dizziness, as blood flow increases to dilated vessels and you lose more fluids via sweating. This can make it difficult to perform certain tasks.

In extreme heat, your body can also experience heat edema, when it dilates blood vessels to try to get as much heat away as possible. This can cause blood to pool in your hands and ankles, as gravity goes to work on the larger blood vessels.

40°C (104°F)

The body may try to get water from different parts of the body, including your fat, muscles, kidneys, and bloodstream, at about 40°C (104°F). With less and less water available, some of your vital organs may start to shut down, including your brain.


If the temperature rises further, then your body can start to shut down, as cells in your body deteriorate. When the body can no longer continue pumping blood to the skin, at temperatures of about 41°C (105.8°F), then you can no longer sweat.

High internal temperatures in your body will also start increasing the pressure in your skull, as blood flow to your brain decreases. This can cause damaged tissue to enter your bloodstream and lead to kidney failure. Higher temperatures, up to 49°C (120°F) or more, can destroy cells in your body and cause permanent damage.

This is heat stroke, and the outcome is not great. It has about a 10 percent mortality rate, with young, elderly, and obese people particularly at risk.

If you experience just some of these symptoms, then it’s advised you get medical aid as soon as possible. You should move to a cooler location, remove clothes, and apply cold cloths to your head, face, and neck. And of course, drink lots of water.


As temperatures continue to rise around the world, more and more people are going to be at risk of heat-related illness. Remember to keep cool, stay safe, and seek help if needed.


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  • heat stroke